Although schistosomiasis is a disease of increasing importance in many tropical areas, the development of biological control methods is impeded by inadequate knowledge of the relationships between the parasite and intermediate host snails. New approaches are needed to develop such means of control. Our goal is increased understanding of the snail-schistosome system by isolating its elements in vitro. Results obtained in our laboratory show that cultures of cells from embryonic Biomphalaria glabrata snails are readily obtainable under proper conditions. We plan to improve methods so that continuous cell lines are established and maintained through numerous subcultures. Specific studies with such cell lines will include chanracterization of the cells, minimalization of the medium, and the development of techniques for cryopreservation and shipment. When these aims have been accomplished, the whole may be repeated using cells from non-host stocks of snails of the same or related species. Sporocysts of Schistosoma mansoni have been maintained by us in axenic media and in arthropod cell cultures, but with limited development. We plan to extend our work in this area to prolong survival and augment development of cercarial embryos in germinal masses, with the aim of producing infective cercariae in vitro. Specific studies with cultured sporocysts will extend current autoradiographic tracing of incorporation of tritiated thymidine, and include other isotopes as well. A combination of snail cell cultures and larval schistosomes will come close to the "artificial snail" and permit more precise studies such as the following: the basis of specifity and compatibility of host and parasite; nutritional requirements of each and of the combination; hormonal effects of each upon the other; the mode of action of drugs and molluscicides; incorporation of specific substances from the medium; effects of inhibitory microorganisms such as microsporidia or viruses; and embryonic development of the germinal masses.